The present invention relates to DC to DC converters, and in particular, to multi-phase converters which produce a DC output voltage at the common output of a plurality of coupled switching power supplies, for example, a plurality of buck converters.
Multi-phase converters are known. In a typical multi-phase converter, for example, a multi-phase buck converter, a plurality of buck converters are provided each having their output inductors coupled to the output node. In a typical application, each buck converter is controlled by a control circuit and may be operated such that a control switch of each buck converter switching stage is turned on at a different time than the other phases. In this way, each phase sequentially provides power to the load, reducing ripple and reducing the size of the output capacitance.
When multi-phase converters are constructed, it is necessary to be able to control the frequency and phase of each of the output switching converters forming the multi-phase converter. In the past, this has been done by employing a single wire bus using an analog 50% duty cycle triangle wave. There were deficiencies in the previous implementation including the following.
(1) Two external resistors are required per phase to program the phase delay. These resistors cost money, require PCB area, increase PCB layout complexity, are a source of potential failure, and their values must be calculated increasing design complexity.
(2) The accuracy of analog programming of phase timing is degraded, there is non-ideal ramp linearity, component tolerance issues, and noise.
(3) Phases can not be programmed to go on near the peak and valley of the triangle wave leading to inherent phase timing errors in some systems.
It would be desirable to provide a multi-phase converter that solves these problems.